Physiological and transcriptomic analyses reveal the mechanisms underlying leaf color variation in zebra-striped mutants of oat (Avena sativa)

Leaf color mutants serve as valuable models for investigating chloroplast development, chlorophyll metabolism, and photosynthetic regulation. However, research on oat mutagenesis remains limited, and the physiological and molecular effects of leaf color mutations in oats are not fully understood. The zebra-striped oat mutant, derived from the wild-type Everleaf via sodium azide (SA) mutagenesis, exhibits distinct white leaf stripes, impaired pigment accumulation, and reduced photosynthetic efficiency. This mutant serves as a model to investigate the underlying molecular mechanisms of pigment biosynthesis and photosynthetic efficiency, offering valuable resources for oat molecular breeding and the development of specialty varieties. The zebra-striped mutant displays a significant reduction in most pigments, particularly carotenoids (43.80% reduction), while chlorophyll b remains largely unaffected. Photosynthetic efficiency and chlorophyll fluorescence parameters are substantially impaired, resulting in stunted growth and poor agronomic performance, with a 16.95% decrease in main panicle seed number and a 26.59% reduction in seed weight of the main panicle. Transcriptome analysis revealed 1,958 DEGs between the mutant and wild-type, including 571 up-regulated and 1,387 down-regulated genes. These DEGs were enriched in GO terms related to chlorophyll biosynthesis, chloroplast function, and carbohydrate binding. KEGG pathway analysis implicated these genes in chlorophyll and carotenoid biosynthesis (e.g., CHLD, POR, ZDS, BCH), photosynthesis, and photosynthetic carbon fixation. Additionally, 36 DEGs in the starch and sucrose metabolic pathways were down-regulated, leading to inhibited starch and sucrose metabolism. qRT-PCR validated reduced expression of key genes (CHLD, POR, LHCB1), confirming their role in the mutant phenotype. The zebra-striped phenotype results from disruptions in pigment synthesis, metabolic pathways, and photosynthetic carbon fixation, leading to reduced chlorophyll content, impaired photosynthesis, and decreased growth and yield. Leaf color variation leads to downregulation of related genes, thereby affecting chlorophyll and photosynthetic metabolism in oats, as well as starch and sucrose metabolism. These findings provide important genetic resources and phenotypic markers for oat breeding programs, contributing to our understanding of chloroplast development and photosynthetic efficiency.